Acetylene gas is a chemical compound C.sub.2 H.sub.2 which may, under pressure, decompose with explosive force, tending to disassociate violently into its constituents. This may be effected by ignition or by shock. Acetylene is usually maintained in a steel tank which has a cement filler of a porous charcoal monolithus or calcium silicate. Such filler is saturated with acetone, in which the acetylene actually dissolves. There is a requirement that the cement filler be absent void where free acetylene in gaseous form can collect. In volumes of over one cubic foot at pressures of over 30 psi, free acetylene can explode from shock only, no fire being required. Thus, acetylene must be contained in a cement lined cylinder and used at pressures below 30 psi. It may be stored in such cylinders at 250 psi, at 70.degree. F. A fusible plug is used with a melting temperature of 212.degree. F. for protection in the event of high temperature, fire and the like. 15 psi gauge pressure has been found to be a safe working limit for use. Therefore, there is a need for a pressure regulator to reduce the pressure from tank pressure to a lower gauge pressure such as 15 psi to permit safe use of acetylene gas.
Acetylene is a non-toxic gas and has been used as an anesthetic, but can cause asphixiation in a confined area without breathing air of at least 18% oxygen. It takes between 2.5 and 81% by volume of air to ignite. Ignition can be effected by low energy spark. The acetylene has an etheral garlic-like smell and can cause dizziness, unconsciousness or even death. Therefore, the equipment associated with the storage and transmission and use of acetylene must be leakproof. If acetylene is withdrawn from its tank at a rate in excess of 1/7 cylinder capacity per hour, protective acetone may exude from the cylinder, thus reducing its protection. Under certain conditions, acetylene forms readily explosive compounds with copper, silver and mercury. Therefore, contact with these metals, their salts, compounds and high concentration alloys must be avoided. Contact with highly caustic salts or solutions or contact with other materials corrosive to copper or copper alloys can render otherwise acceptable alloys unsatisfactory. The presence of moisture, certain acids or alkaline materials tends to enhance the formation of the dangerous acetylides.
In normal use, acetylene gas is supplied from steel tanks provided with proper on/off valves per standards of the Compressed Gas Association (CGA) and of proper size and style for the gas being used. Pressure regulators have been developed in an attempt to meet these standards and to provide a pressure regulator which is both leakproof and compatible to the gas. One such pressure regulator is the subject matter of U.S. Pat. No. 3,972,346 to Alex F. Wormser issuing Aug. 3, 1976. That pressure regulator is constituted by a valve body bearing a longitudinal bore within which is threadably positioned a tire valve bearing centrally a spring biased tire valve center pin or stem which selectively permits or closes off the flow of fluids through the valve structure with the valve being positioned intermediate of a gas inlet and a gas outlet. The end of the valve stem projects axially of the tire valve casing and a cup-shaped slide is carried by the valve body and spring biased by a compression spring, these elements being located within a regulator body chamber on the outlet side of the regulator, and wherein the gas pressure within the regulator chamber acts oppositely to move the slide and the compression spring in a direction tending to close the valve, while acting on the valve stem member tending to maintain the tire valve in open position.
The pressure regulator of U.S. Pat. No. 3,972,346 advantageously employs a tire valve as a single valve element between the tank or supply side and the outlet. However, the regulator is complicated and costly due to the nature of the slide, the compression spring, and the necessary seal between the axially shiftable slide and the fixed valve casing. Such a regulator in employing a slide and other similar regulator employing pistons or diaphragms have great difficulty with leakage and require the use of O or quad rings or lip seals, which require gas pressure to make them effective. The seals which deteriorate over time, permit small leaks to exist. Further, such regulators as that of U.S. Pat. No. 3,972,346, even when leak-free at the time of manufacture, can develop leaks from surface damage, poor material selection and from effects of aging and non-compatibility of materials.
It is, therefore, a primary object of this invention to provide an improved gas pressure regulator, more particularly for acetylene gas regulation which is of simplified construction, low cost, is devoid of main pressure control slides, requires no sealing rings or special seals and no diaphragm and has no separate springs for pressure balance, which is leak-proof and which is formed of materials which will not react with acetylene gas.
It is a further object of this invention to provide an improved pre-set gas pressure regulator which employs a tire valve as a singular valve for reducing pressure from the inlet to outlet passage, and wherein tire valve opening pressure is pre-set and operation is controlled by a leakproof metal bellows which acts as a spring both in extension and compression and which instantly closes the valve to any pressure above the pre-set value.